With all that's been said, would a street car with 255 square, eibach fsb, non-aero and standard Ohlins be better suited with the standard staggered spring rate (10/8k) or a square spring rate (10/10k)?

After moving from a 225/255 to 255/255 tire setup, the car handled significantly different; all else held constant. I swapped the eibach fsb on and the front-end feeling returned, however the rear still retained a "slippery" oversteer-ish feeling. I kept the rebound adjustment at 10 turns from full stiff. I was advised to stiffen the rear by 2 clicks and loosen the front by 1.

 

STR cars all run 255 square, and just about everyone runs stiffer front springs than rear. (Mine are about 13.5k/10k.) True, most who do so are simply emulating others, but there are a number of high level autocrossers who have tested various setups and come up with this.

Are you still running the stock rear sway bar? Sounds like you would benefit from moving to a thinner rear bar, like the Miata bar a lot of people use, or the Karcepts rear. (To start with you could just disconnect your rear bar and see if that improves the feel.) Especially if your spring rates are 10k/10k, I don't think you'd want any rear bar.

 

 

14k non staggered here

Sways staggered.

 

F1 cars also have the wheelbase of a crew cab pickup (about 145"). And even with 800 hp, they use significantly different aero and suspension setups depending on the speed and design of the track.

The answer here is more complicated. Many larger tires may have a problem getting up to and maintaining temperature. Some, designed for heavier cars may not work that well on the S2000. Note that the BFG Rival S 1.5 was designed for lighter cars, and if you remember the RE-11 later came in an RE-11a for lighter cars, including the S2000.

Many have different diameters affecting suspension geometry. On lowered S2000s without a drop spindle, the geometry is pretty off anyway. The OEM Torsen differential requires weight on the inside wheel to work, limiting rear roll stiffness.

With the right setup, most reasonable combinations probably can be made to work, whether staggered or square. On most tracks, a 285/30-18 or 295/30-18 probably would beat a 255/35-18. However, depending on the suspension setup the shock may not be right for the heavier wheel/tire combo or the suspension geometry and stiffness may not be able to take advantage of the wider tread. A 255/40-17 (or Hoosier 275/35-17), with its taller sidewall, may adapt better to a suspension geometry that puts the tire at a less optimal angle.

The Wisefab suspension with Karcepts bars, OE Giken diff, Penske shocks, etc. could make the wider square setup faster or a 255/285 faster than a 255 square. Lacking that or equivalent, it is hard to imagine any 18" wheel setup being faster than a 255/40-17 (or 275/35-17) square properly setup. It's the taller sidewall.

Unless rolling drag (the tires are in fenders minimizing aero drag) became a serious issue, it is hard imagining where lateral grip isn't the limiting factor. Few NA S2000s generate enough power to overpower the rear tires at road course speeds on most tracks. That is, does the car spin the tires on a 2-3 shift?

About 10/10ths. There is 10/10ths when control is most important (e.g., an LMP car in endurance events) and when speed is important (e.g., an F1 car). Unless competing in a class where those 10ths of a second count, few drivers sacrifice control for speed. Note that F1 drivers are arguably the best in the world, but in practice and occasionally in qualifying, they have offs, spins, and crashes.

 

^^ I think you meant 275/40/17?

275/35/17 Hoosiers are a smaller diameter then a 255/40/17.

 

The 275/35 is 24.6"-24.7" in diameter, the 275/40-17 is 25.6"-25.7" in diameter. The latter exasperates the S2000 suspension geometry issue by requiring more lowering to achieve the same ride height and exasperates the front fender clearance issues.

The Hoosier A7 and R7, and the Maxxis RC-1 all come in the 275/35-17 size. Those tires are all slicks. The size would be too wide for NASA TT5.

 

Yes. I have an 07 and am using the factory RSB. I'm trying to regain the feeling of control that the car exhibited before moving to a square setup. I could drive the wheels off of it with the staggered setup, but now my confidence is robbed. The rear doesn't feel planted. It's as if the roll ratios front to back aren't balanced. The rear just wants to roll over into a corner. I feel like I need more rsb or higher spring rates.

I'm trying to figure out how to restore the handling balance, but with the added front grip to brake later/deeper and without push.

 

I understand the size measurements, which is why i pointed it out. Your previous statement seemed to contradict this, or maybe you just worded in a way I didn't interpret right.

 

In your previous message you said the rear "still retained a 'slippery' oversteer-ish feeling". That sounds like too much rear bar to me, not too little. Since you've got the stock rear bar on it now (I assume FSB was a typo, since you said you'd moved to an Eibach FSB?) I'd just try disconnecting it to start. I bet you'll find the rear feels more planted. (Of course, you'll also get more roll; if that's a problem you could compensate with more front bar, assuming it's still biased toward oversteer, and/or with dampers to some extent.) Or change your spring rates of course, but presumably it makes more sense to try to dial things in with what you have first.